To cook rice and pigeon pea lentils (arhar dal) in a clip-on type pressure cooker, start by washing 1 cup of split pigeon peas and soaking them for about 30 minutes if you prefer. In the cooker, heat a little oil and add spices like cumin seeds and chopped onions, sautéing until the onions are golden. Then, add chopped tomatoes, turmeric, salt, and the rinsed lentils along with 3 cups of water. If you're cooking rice simultaneously, place a separate bowl with rinsed rice and water on a trivet above the lentils. Close the lid securely and cook on high heat until you hear one whistle, then reduce the heat and simmer for about 4-5 minutes. After cooking, let the pressure release naturally for about 10-12 minutes before opening the lid. Your delicious rice and dal are now ready to serve!